Runnaway Turbo

[billy1971]

First i have a 1995 3500, crew dually. I had to replace the 6.5 a year ago because of a lower radiator hose. I did this with a rebuilt N/A 6.2 directly out of the military crate it came in. Although I had some serious concerns about this conversion at first this actually has been a great move. I installed the EGT, and Boost gauges and monitor them faithfully. I haul cars with my truck and the increased preformance is great. My problem is that without warning, while accellerating the boost will instantly go from 8 psi to 22 psi. The increased accereration is actually pretty impressive but with no control is actually dangerous and when it starts bucking, unconfortable.

Always during acceleration, no eccesive smoke noticable, i let off the pedal and it goes back to idle when I accelerate again it might or might not still be in high boost, When bucking it might jump two times, then run strong for five seconds then normal then run fine for two days or two weeks. I'm just not sure if this is the turbo, turbo controls, or what ever tells this thing to turn on and off.

[greatwhite]

Are you still running the stock vacuum system?

There are a couple things that could go wrong there.

The wastegate solenoid could be sticking. Or the wastgate itself could be sticking.

Another possibility might be an odd pmd failure where it allows too much fuel which causes the turbo to accelerate.

Last think I can think of is the boost sensor sending erratic readings to the PCM.

Use the paper clip trick and see if any fault codes are lurking in the PCM.....

[billy1971]

Yes the vacuum is stock, it is a new pump. I'm guilty of buying used PMDs so I'm not real sure about that. I will check for codes, I have been getting some check engine lights they just done stay on. Can the waist gate actuator activate as fast as this this is bucking?

[DmaxMaverick]

Bucking is fueling, not wastegate. The wastegate can actuate that fast, but it takes several seconds for the exhaust gasses to spool the turbo. Bucking and overspeed is likely going to be electrical connection and/or PMD issues. 22 PSI is (almost) impossible with stock fuel rates and OEM equipment, especially that quickly. Something else, or a combination of things is wrong. Pull the code(s), pick a starting point at one end of the system, and work your way through it.

[billy1971]

Thanks to both who responded to my issues, that makes sinse. I'll be pulling the codes tonight and starting from there.

[billy1971]

OK, well I was fooled again. I had plenty of codes that all lead to a electrical/electronic issue as you suggested.

codes are- 18, 19, 35, 47, 54, 78, and 81. I found all but the #81 still dont know what that one is.

I just purchased a "New" aftermarket PMD from a friend, installed a new #9 PMD resistor i had put back. After checking all connections on the sensors listed i installed the PMD on the PMD cooler and test drove the trk. No noted change in performance, but no problems either. Of course remember this thing can go for days without a sign of problems before it bucks and jumps for 60 miles. I've had five or six PMD failures in the past but they either worked or didnt work never had one do stupid stuff like this. Not really sure how to test the Crank and pump cam sensors. I will be taking the truck out on a 600 mile run this friday. does anyone see anything else I need to look at. Still open for suggestions, I dont like doing my troubleshooting on the road.

[billy1971]

One last note, jus finished changing out the harmonic balancer pully. The rubber bushing had failed and was allowing it to knock pretty loud. Not sure if this could allow for some erronous sensor inputs??

[a5150nut]

Is you PMD ground on the pump? It should be.

Have you cleaned all electrical connections with contact cleaner and reassembeled ? No loose conections in the extension cable?

Just the first thoughts that come to mind.

[Kennedy]

Sounds like you are due for a new DS4 pump. Be sure to run a good additive in the new one or it will liley end up in the same boat as this one.

[DmaxMaverick]

Sounds like you are due for a new DS4 pump. Be sure to run a good additive in the new one or it will liley end up in the same boat as this one.

Possibly, but it only explains a couple codes. Too many other unrelated codes that need to be explained, and since we are assuming (yeah, I know....) these all started showing up at similar relative times, it should be related to a similar incident or failure. This screams grounds and/or electrical harness/connector problems. Similar to what might happen if a rodent took up interior decorating under the hood. Been there. Done that.

Clean and verify all grounds, and look around for chafed/damaged harness, connectors and looms while you're in there. Use a flashlight and mirror to see around corners and under stuff. I suggest focusing on PCM connectors and related harnesses. Open, clean, inspect (verify no spades/pins have been pushed out or bent), grease (dielectric) and reconnect every connector you find. Also watch for burned connectors and wires. I know it sounds tedious, and it is, but a necessary diagnostic step. Wild grounding can cause circuits to overheat, that would otherwise carry the load fine.

[billy1971]

Hey! this is good stuff! I installed an extension harness about 6 months ago along with the new PMD cooler. Harness failed in three days, cost me a nasty towing bill. I just plugged it back in at the pump and have it sitting on a shop towel for vibration. Havent had the desire to try a fancy installation again yet. grounding this never crossed my mind, guess i just assumed it was grounded through the harness. I will ground this properly before I leave out tonight.

I did take the truck out for a short haul today (60 miles) without incident.

[a5150nut]

You can make your own harnes. Match wire size, solder and heat shrink connections. Did my own 10 or 11 years ago. Mounted mine in front of left battery over an opening in the front fire wall. There was already a hole in the radiator suport to screw it to.

[greatwhite]

Clear your PCM trouble codes, that many is very suspect.

Run it again and see what returns.

If you get that laundry list of codes again then the ground for the PCM (passenger side rear of intake manifold) is highly suspect....

[Kennedy]

The DTC 18 leans me towards a pump issue although it is possible that if some other 5v device on the same reference signal is shorted it could affect this.

I've never used more grounding to the PMD than what the factory harness provides to the pump body.

There are a lot of cheap harnesses out there and apparently it's becoming obvious why. I've been contacted by China to sell them, but they are clearly substandard. I'll stick with my US built units that have a stellar track record.

[greatwhite]

Another thing to note; You need to get your pmd into a source of some type of cooling.

Without it being mounted on the pump or one some type of suitable heat sink, you run the risk of overheating it.

Every time you allow it to operate above it's specified max temperature you are taking life off it.

It may not fail today, it may not fail tomorrow but it will fail prematurely.

Just something to think about.....

[lilymonster]

Hey billy, sorry to hear about these struggles-- sounds like you do have some very solid ideas to pursue to get things sorted out. Two things guys,

1. Please clarify for me this PMD grounding thing... it DOES ground only through the harness itself correct? There is no ground on the body of the unit itself from my understanding.

2. Billy, if you don't mind, what was the brand/type/source of the harness that you had that failed within 3 days? There are a lot of them for sale out there and itd be nice to know which to avoid...

[greatwhite]

Hey billy, sorry to hear about these struggles-- sounds like you do have some very solid ideas to pursue to get things sorted out. Two things guys,

1. Please clarify for me this PMD grounding thing... it DOES ground only through the harness itself correct?

Yes, for the function that it is designed to perform. Through the eyelet that attaches to the top of the IP.

There is no ground on the body of the unit itself from my understanding.

Nope.

2. Billy, if you don't mind, what was the brand/type/source of the harness that you had that failed within 3 days? There are a lot of them for sale out there and itd be nice to know which to avoid...

One word of advice to heed; No eBay cables or PMD's.....unless you're picking up a used PMD to just test with. Even that is a crap shoot....

Copied from another place on the web, use at your own risk:

A- Green wire from puter. Tells it what to do.
(Fire the injectors)

B- Red wire goes to back of pump to the poppet valve solenoid
(Triggers the firing)

C-Black wire goes to puter so puter has a ground like PMD
(Good grounds make happy puters)

D- Pink wire goes to ignition and the electric shut-off solenoid
(That silver shiny cylinder thing up front thing) 12volts or better on a good day.

E-Another red wire, goes to puter and tells it what the pulse width is to the puter.
(So it can throw up a code when the pump or PMD is shot. 35 or 36 take your pick)

F- Another black wire, goes to back of pump to the poppet valve solenoid
(grounds the solenoid so it will fire when the PMD sends it some juice)

[racedaymechanic]

The DTC 18 leans me towards a pump issue although it is possible that if some other 5v device on the same reference signal is shorted it could affect this.

I've never used more grounding to the PMD than what the factory harness provides to the pump body.

There are a lot of cheap harnesses out there and apparently it's becoming obvious why. I've been contacted by China to sell them, but they are clearly substandard. I'll stick with my US built units that have a stellar track record.

Ive made a couple for myself, I used 16 gauge Milspec wire, gold plated terminals for the Grey Pmd and Metripac connectors, They are bulletproof I wanted 7 1/2 feet because of the routing, By the way did you get the Glow Plug Harness I sent you John?

[racer55]

What brand PMD did you replace with new?

Flight Systems PMD's were known for runaway conditions if they came from a bad batch during manufacture-if it doesn't say stanadyne,then it is a flight systems no matter the branding.

[Kennedy]

By the way did you get the Glow Plug Harness I sent you John?

Yes nice looking piece.

I need to get these listed on the store.